Cant copy files from internal storage

I have some files on the internal storage, from the downlad folder, that i want to copy to my sdcard, but theres no file explorer that will let me do it. I've tried both Root Browser and Root File Manager. They just give me an error saying 'Operation Failed!".

If i plug it into my PC through MTP and tries to copy the files, either to the SDcard or my own computer, windows 8 gives me an "Unspecified error" or saying "The device is off, or file not found" (or similar).

What is wrong? Why cant i move the files from the internal storage? Hope you can help me.

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